Compass and Magnetism

PERMANENT MAGNETISM

• (HARD IRON)) - RETAINED FOR LONG PERIOD WITHOUT APPRECIABLE CHANGE UNLESS DEMAGNETISED.

INDUCED MAGNETISM

• (SOFT IRON) – ACQUIRED BY A PIECE OF MAGNETIC MATERIAL WHILE IN MAGNETIC FIELD.

RESIDUAL MAGNETISM

• RESIDUE OR DEMAGNETIZATION REMAINING MAGNETISM AFTER REMOVAL.

SUB PERMANENT MAGNETISM

• MAGNETISM IN THE INTERMEDIATE IRON OF THE SHIP WHICH TENDS TO

CHANGE AS A RESULT OF VIBRATION, AGING OR CRUISING IN SAME

DIRECTION FOR LONG PERIOD BUT DOES NOT ALTER IMMEDIATELY.

EXITEXIT

ENTERENTER

BLUEBLUEMAG.MAG.POLEPOLE

REDRED MAG.MAG. POLEPOLE

BASIC PRINCIPLEBASIC PRINCIPLESAME POLARITY – REPELSAME POLARITY – REPELDIFF. POLARITY - ATTRACTDIFF. POLARITY - ATTRACT

NMP (BLUE)NMP (BLUE)

SMP (RED)SMP (RED)

EARTHEARTH

NORTH NORTH SEEKING SEEKING

POLEPOLE

SOUTH SOUTH SEEKING SEEKING

POLEPOLE

ENTERENTER

LEAVINGLEAVING

VARIATION• AN ERROR CAUSED BY EARTH’S

MAGNETIC FIELD. (EXTERNAL)

DEVIATION• AN ERROR CAUSED BY LOCAL OR

SHIP’S MAGNETISM. (INTERNAL)

• VARIATIONVARIATION• 1.1. ANGULAR

DIFFERENCE BETWEEN TRUE NORTH AND MAGNETIC NORTH.

• 2.2. DUE TO EARTHS MAGNETIC FIELD.

• 3.3. CHANGE AS YOU CHANGE POSITION.

• 4.4. “NO”, CANNOT REMOVED.

• DEVIATIONDEVIATION• 11 ANGULAR

DIFFERENCE BETWEEN COMPASS NORTH AND MAGNETIC NORTH.

• 22 DUE TO LOCAL MAGNETISM

• 33 CHANGE AS YOU CHANGE HEADING.

• 44 “YES”, CAN BE CHANGE.

• CORRECTING COMPASSCORRECTING COMPASS

• C CAREFULLCAREFULL• D (+) E D (+) E DRIVER DRIVER • M (-) W M (-) W MANEOUVERMANEOUVER• V V VIRGINVIRGIN• T T TENDERLYTENDERLY

• UNCORRECTING COMPASSUNCORRECTING COMPASS

• T T TRUETRUE• V V VIRGINVIRGIN• M (REV.) M (REV.) MAKESMAKES• D D DULLDULL• C C COMPANION COMPANION

SOFT IRONSOFT IRON

VERTICAL HEELINGVERTICAL HEELINGMAGNET – N/S MAGNET – N/S ““JJ””

QUADRANTAL SPHEREQUADRANTAL SPHERENE/SE/NW/SW NE/SE/NW/SW ‘‘DD ””

ATHWARTSHIP MAGNET – N/S ATHWARTSHIP MAGNET – N/S ““CC ””FORE & AFT MAGNET- E/W FORE & AFT MAGNET- E/W ““BB ””

FL

IND

ER

S B

AR

/ SO

FT

IRO

N –

FL

IND

ER

S B

AR

/ SO

FT

IRO

N –

E/W

E

/W ““ EE

””

At the Magnetic EquatorMagnetic Equator, the attraction of the compass

needle towards the north and north and south poles is equalsouth poles is equal and the needle remains unbiasedremains unbiased. As the compass is moved either

north or south of the magnetic equator, the attraction to the

nearest pole is increased, thus the needle will be biased

towards the nearest pole. This phenomenon is called

Magnetic DipMagnetic Dip.

MAGNETIC COMPASS• USES 45% OF GRAIN ALCOHOL

(ETHYL ALCOHOL) & 55% OF DISTILLED WATER OR KEROSENE TYPE FLUID WHICH IS NOT INTERCHANGABLE.

COEFFICIENTS

• IS THE ANALYSIS OF MAGNETIC PROPERTIES OF A VESSEL IN THE COURSE OF MAGNETIC COMPASS ADJUSTMENTS. THE VALUES ARE

DETERMINED FROM THE DEVIATION OF AN ADJUSTED COMPASS.

KEYWORDS

• COEF. A CONSTANT IN ALL HEADING.

• COEF. B SEMI CIRCULAR DEV./SINE.

• COEF. C SEMI CIRCULAR DEV./COS.

• COEF. D QUADRANTAL DEV./ SINE.

• COEF. E QUADRANTAL DEV./COS.

• COEF. J 1 DEG. HEEL AT 000º HDG.

DEFINITION OF TERMS• 1. 1. AGONIC LINEAGONIC LINE – LINE CONNECTING POINT

OF ZERO VARIATION.• 2. ACLINIC LINEACLINIC LINE – LINE CONNECTING POINT

OF ZERO DIP.• 3. 3. ISOGONIC LINEISOGONIC LINE – LINE CONNECTING

POINT OF EQUAL MAGNETIC VARIATION.• 44. . ISOCLINICAL LINEISOCLINICAL LINE - LINE CONNECTING

POINT OF EQUAL MAGNETIC DIP.• 5. 5. ISODYNAMIC LINEISODYNAMIC LINE – LINE CONNECTING

POINT OF EQUAL INTENSITY.

GYROSCOPEGYROSCOPE

GyroscopeGyroscope is a device for measuring or maintaining orientation, based on the principle

of conservation of angular momentum. The essence of the device is a spinning wheel essence of the device is a spinning wheel on an axleon an axle. The device, once spinning, tends to resist changesto resist changes to its orientation due to the angular momentum of the wheel. In physics

this phenomenon is also known as Gyroscopic Inertia Gyroscopic Inertia or or Rigidity in SpaceRigidity in Space..

A Gyroscope in Gyroscope in operationoperation with

freedom in all three axis. The rotor will

maintain its spin axis direction regardless of the orientation of the

outer frame.

PrecessionPrecession refers to a change in the direction of

the axis of a rotating object. In certain contexts,

"precession" may refer to the precession that the Earth experiences, the effects of this type of

precession on astronomical observation, or to the precession of orbital

objects.

• 1. This is the 1. This is the process of eliminating the process of eliminating the deviationdeviation by introducing a magnetic by introducing a magnetic field at the compass that is equal in field at the compass that is equal in magnitude and opposite in polarity to magnitude and opposite in polarity to that of the vessel.that of the vessel.

• A. compass and magnetism

• B. compass deviation

• C. compass coefficient

• D. compass adjustment

• 2. It is the 2. It is the variation changes thatvariation changes that occur occur twice dailytwice daily due to lunar and solar tides due to lunar and solar tides in the earthin the earth’’s atmosphere.s atmosphere.

A. solar changes

B. diurnal changes

C. lunar changes

D. tidal changes

• 3. The 3. The EARTHEARTH’’S magnetic poleS magnetic pole in the in the Northern Hemisphere (North Magnetic Northern Hemisphere (North Magnetic Pole) has what Pole) has what kind of magnetismkind of magnetism??

• A. South magnetism

• B. North magnetism

• C. North magnetic field

• D. South magnetic field

• 4. It is the 4. It is the ratio of the strength of the ratio of the strength of the magnitude field inside the metalmagnitude field inside the metal to the to the strength of the external field.strength of the external field.

• A. Gauss

• B. Compensation

• C. Permeability

• D. Corrections

• 5. This 5. This phenomena phenomena occurs whether occurs whether electrical charges is moving along a electrical charges is moving along a wirewire, flowing with the magma of the , flowing with the magma of the earthearth’’s core encircling the earth at high s core encircling the earth at high altitudes as a steam of charged altitudes as a steam of charged particles, or rotating around the particles, or rotating around the nucleus of an atom.nucleus of an atom.

• A. Magnetic field

• B. Sub – permanent

• C. Induced

• D. Magnetism

6. What 6. What instrumentinstrument that that measures measures

magnetic fieldsmagnetic fields??

• A. Magnetmeter

• B. Magnenometer

• C. Magnetometer

• D. Magnetic field meter

7. In what 7. In what direction is the magnetic direction is the magnetic compass pointing if it is influenced compass pointing if it is influenced by the earthby the earth’’s magnetic fields magnetic field and is and is free from the magnetic influence of free from the magnetic influence of surrounding structures?surrounding structures?

A. Compass NorthA. Compass North

B. True NorthB. True North

C. Magnetic NorthC. Magnetic North

D. Geographic NorthD. Geographic North

8. What is the 8. What is the semi-circular deviationsemi-circular deviation which is proportional to the which is proportional to the sinesine of of the compass heading?the compass heading?

• A. Coefficient B

• B. Coefficient C

• C. Coefficient D

• D. Coefficient E

9. How are compass errors applied from 9. How are compass errors applied from

compass directions to true directionscompass directions to true directions??

• A. Add easterly and subtract westerly

• B. Add westerly and subtract easterly

• C. Add westerly deviation

• D. Add westerly variations

10. Which deviation change signs 10. Which deviation change signs

approximately each 90 degrees change approximately each 90 degrees change

of headingsof headings caused by induced caused by induced

magnetism in horizontal soft iron?magnetism in horizontal soft iron?

• A. Residual deviation

• B. Constant deviation

• C. Semi-circular deviation

• D. Quadrantal deviation

11. On which direction does 11. On which direction does magnetic magnetic

line of forcesline of forces flow in the flow in the vicinity of vicinity of

magnetic equatormagnetic equator??

• A. Vertically upward

• B. Downward towards the pole

• C. Upward towards the pole

• D. Parallel to the surface

12. 12. VariationVariation is a compass error that is a compass error that you:you:

• A. cannot correct

• B. can correct by adjusting the compass

card

• C. can correct by adjusting the

compensating magnets

• D. can correct by changing the ship’s

heading

13. 13. Deviation changes with a changeDeviation changes with a change in in _____._____.

• A. latitude

• B. heading

• C. longitude

• D. sea conditions

14. As a vessel changes course to 14. As a vessel changes course to

starboard the starboard the compass card in a compass card in a

magnetic compassmagnetic compass::

• A. turns counter clockwise to port

• B. also turns to starboard

• C. remains aligned with the compass

north

• D. first turns to starboard then

counterclockwise to port

15. By convention the 15. By convention the south seeking south seeking

ends of a compass magnetsends of a compass magnets are colored are colored

____.____.

• A. blue

• B. red

• C. white

• D. black

16. 16. MagnetsMagnets are placed in horizontal are placed in horizontal

trays in the trays in the compass binnacle to compass binnacle to

compensate forcompensate for the: the:

• A. permanent magnetism of the vessel

• B. magnetic fields caused by electrical

currents in the vicinity

• C. change in the magnetic field when the

vessel inclines from the vertical

• D. induced magnetism in the vessel’s

horizontal soft iron

17. Which statement about the 17. Which statement about the flinders flinders bar of the magnetic compass is correctbar of the magnetic compass is correct??

• A. It compensates for the error caused by the circular error caused by the earth’s magnetic fields

• B. It compensates for the error caused by heeling of the vessel

• C. It compensates for the quadrantal deviation

• D. It compensates for the error caused by vertical component of the earth’s magnetic field

18. To 18. To expedite the adjustmentexpedite the adjustment at sea at sea when you are to about to go to sea for when you are to about to go to sea for compass adjustments in what ordercompass adjustments in what order should the following be made?should the following be made?

• A. Flinders bar first, then the spheres, then the heeling magnets (FSH)

• B. Heeling magnets first, then the flinders bar and spheres (HFS)

• C. Flinders bar first, then the heeling magnets and spheres (FHS)

• D Spheres first, then the flinders bar and heeling magnets (SFH)

19. What is the 19. What is the horizontal intensityhorizontal intensity’’ss

component component along a geographic or true along a geographic or true

meridianmeridian??

• A. East component

• B. West component

• C. North component

• D. South component

20. What do you call the coefficient 20. What do you call the coefficient

which is which is semi-circular deviationsemi-circular deviation and is and is

proportional to the proportional to the sine sine of the compass of the compass

heading. Itheading. It’’s maximum on the compass s maximum on the compass

heading East or West and zero on heading East or West and zero on

compass heading North and South?compass heading North and South?

• A. Coefficient A

• B. Coefficient B

• C. Coefficient C

• D. Coefficient D

21. 21. Deviation is causedDeviation is caused by _____. by _____.

• A. magnetic influence inherent to that

particular vessel

• B. changes in the earth’s magnetic field

• C. nearby magnetic land masses or

mineral deposits

• D. the magnetic lines of force not

coinciding with the lines of longitude

• 22. It is an error on the magnetic compass 22. It is an error on the magnetic compass when the when the lubber line is not correctly lubber line is not correctly alignedaligned with the fore and aft axis of the with the fore and aft axis of the craft.craft.

A. sine wave error

B. double sine wave error

C. hard iron deviation error

D. constant error

• 23. It is the 23. It is the direction taken up by direction taken up by longitudinal axis of a compass needlelongitudinal axis of a compass needle when under the influence of the Earthwhen under the influence of the Earth’’s s normal force.normal force.

A. magnetic equator

B. magnetic variation

C. magnetic north

D. magnetic meridian

• 24. A curve passing through 24. A curve passing through places places where there is neither DIP nor where there is neither DIP nor inclinations of the compass needleinclinations of the compass needle..

A. magnetic field

B. magnetic force

C. magnetic equator

D. magnetic variation

• 25. It is the angle through which the 25. It is the angle through which the magnetic meridian is magnetic meridian is mis-aligned withmis-aligned with the true north meridian.the true north meridian.

A. magnetic error

B. variation

C. deviation

D. alignment error

• 26. On a Mercator Chart, the 26. On a Mercator Chart, the compass compass rose will generally indicaterose will generally indicate the: the:

A. variation

B. compass error

C. deviation

D. isobar

• 27. It is the property of the magnetic 27. It is the property of the magnetic compass to compass to retain its magnetismretain its magnetism at a long at a long period of time.period of time.

A. tenacity

B. polarity

C. retentivity

D. permeability

• 28. It represent the 28. It represent the magnetic fluxmagnetic flux density density whereas the strength of the whereas the strength of the magnetic field depends on the material magnetic field depends on the material through which the magnetic flux is through which the magnetic flux is passing.passing.

A. density unit

B. flux unit

C. field unit

D. gauss unit

• 29. 29. By conventionBy convention, the , the EarthEarth’’s norths north magnetic polemagnetic pole is colored: is colored:

A. red

B. white

C. black

D. blue

• 30. Which of the following will be used 30. Which of the following will be used to correct to correct deviation on inter-cardinaldeviation on inter-cardinal headingsheadings??

A. Athwarthship magnets

B. Quadrantal spheres

C. Fore and aft magnets

D. Heeling magnets

• 31. At the 31. At the magnetic equatormagnetic equator, there is , there is no no induced magnetism in the vertical soft induced magnetism in the vertical soft ironiron because: because:

A. The lines of force cross the equator on a

0-180alignment

B. There is no vertical component of the

Earth’s magnetic field

C. The quadrantal error is 0D. The inter-cardinal headings have less

than 1 error

• 32. The points on the Earth32. The points on the Earth’’s surface s surface where the where the magnetic dip is 90magnetic dip is 90 are: are:

A. along the magnetic equator

B. connected by the isoclinical line

C. the isopors

D. the magnetic poles

• 33. The magnetic compass magnets are 33. The magnetic compass magnets are acted on by the horizontal component of acted on by the horizontal component of the Earththe Earth’’s total magnetic force. The s total magnetic force. The magnetic force is GREATESTmagnetic force is GREATEST at the: at the:

A. North magnetic pole

B. South magnetic pole

C. Magnetic equator

D. Magnetic prime vertical

34. If a 34. If a magnetic compass is not magnetic compass is not

affected by any magnetic field other affected by any magnetic field other

than the Earththan the Earth. Which statements is . Which statements is

TRUE?TRUE?

• A. There will be no compass error

• B. Compass north will be the true north

• C. Variation will equal deviation

• D. Compass error and variation are equal

35. What is the term used to identify the 35. What is the term used to identify the

semi-circular deviationsemi-circular deviation which is which is

proportional to the proportional to the cosinecosine of the of the

compass heading where it is maximum compass heading where it is maximum

on the North or South and zero on East on the North or South and zero on East

or West heading?or West heading?

• A. Coefficient “C”

• B. Coefficient “E”

• C. Coefficient “D”

• D. Coefficient “F”

36. What are 36. What are lines connecting points of lines connecting points of

equal magnetic dipequal magnetic dip??

• A. Isogonic line

• B. Isoclinic line

• C. Isophase line

• D. Isodynamic line

• 37. What magnetic 37. What magnetic compass corrector compass corrector cannot be set on a heading of magnetic cannot be set on a heading of magnetic east or magnetic westeast or magnetic west??

• A. Athwartship magnets

• B. Heeling magnets

• C. Fore and aft bar magnets

• D. Quadrantal spheres

• 38. At a distance of several hundred 38. At a distance of several hundred miles above the earthmiles above the earth’’s surface, the s surface, the magnetic fieldmagnetic field surrounding surrounding the earth is the earth is believed to be uniform and centered believed to be uniform and centered around twoaround two ______. ______.

• A. axis poles

• B. magnetic poles

• C. geographical poles

• D. poles

• 39. It is the 39. It is the strength of the field at any strength of the field at any pointpoint, measured in a direction parallel , measured in a direction parallel to the field.to the field.

• A. north intensity

• B. total intensity

• C. parameter P

• D. north component

• 40. It is a valuable reference in 40. It is a valuable reference in navigation, for it navigation, for it provides the directive provides the directive force for the magnetic compassforce for the magnetic compass..

• A. horizontal component

• B. north component

• C. parallel component

• D. east component

• 41. The magnetism in the intermediate 41. The magnetism in the intermediate iron of the ship which iron of the ship which tends to change tends to change as the result of vibration, aging or as the result of vibration, aging or cruising in the same direction for a long cruising in the same direction for a long periodperiod but does alter immediately. but does alter immediately.

• A. permanent magnetismA. permanent magnetism

• B. residual magnetismB. residual magnetism

• C. sub-permanent magnetismC. sub-permanent magnetism

• D. induced magnetism D. induced magnetism

• 42. According to present theory, the 42. According to present theory, the magnetic field around a current-magnetic field around a current-carrying a wirecarrying a wire and the magnetism of a and the magnetism of a permanent magnet are created by permanent magnet are created by moving ______.moving ______.

• A. external field

• B. electrical charges

• C. induced magnet

• D. sub-permanent magnet

• 43. Any piece of metal on becoming 43. Any piece of metal on becoming magnetized will develop magnetized will develop regions of regions of concentrated magnetismconcentrated magnetism called: called:

A. poles

B. magnetic fields

C. magnetic poles

D. induced magnetism

• 44. It is the vertical component of the 44. It is the vertical component of the total intensity where it is total intensity where it is zero at thezero at the magnetic equatormagnetic equator..

A. north component

B. horizontal intensity

C. vertical intensity

D. south component

• 45. It is the 45. It is the strength of the field at any strength of the field at any point,point, measured in a direction parallel to measured in a direction parallel to the earththe earth’’s magnetic field.s magnetic field.

A. total intensity

B. horizontal intensity

C. vertical intensity

D. magnetic intensity

• 46. It is the vertical angle, expressed in 46. It is the vertical angle, expressed in angular units, angular units, between the horizontalbetween the horizontal at at any pointany point and a line force through that and a line force through that point.point.

A. variation

B. magnetic dip

C. vertical angle

D. deviation

• 47. On the earth47. On the earth’’s magnetic field, it is s magnetic field, it is the horizontal intensitythe horizontal intensity’’s component s component perpendicular to the north componentperpendicular to the north component.

A. west component

B. south intensity

C. south component

D. east component

• 48. On the earth48. On the earth’’s magnetic field, it is s magnetic field, it is the horizontal intensitythe horizontal intensity’’s component s component along aalong a geographic/true meridian.geographic/true meridian.

A. north intensity

B. south intensity

C. south component

D. north component

• 49. In 49. In magnetic compassmagnetic compass, what is the , what is the usual usual type of liquidtype of liquid being used? being used?

A. Distilled water

B. Alcohol

C. Mercury

D. Tap water

• 50. It is the direction of the horizontal 50. It is the direction of the horizontal component of the earthcomponent of the earth’’s magnetic field s magnetic field running towards the north magnetic running towards the north magnetic pole.pole.

A. magnetic meridian

B. deviation

C. variation

D. magnetic polarity

51. At the 51. At the magnetic equatormagnetic equator, what is the , what is the direction of magnetic line of forcesdirection of magnetic line of forces??

A. Vertically downward

B. Vertically upward

C. Gradually upward

D. Parallel to the surface

• 52. The earth as a magnet, what is the 52. The earth as a magnet, what is the direction of the earthdirection of the earth’’s field dips at the s field dips at the magnetic pole?magnetic pole?

A. Horizontally upward

B. Vertically downward

C. Parallel to the surface of the earth

D. Gradually upward

• 53. This is the 53. This is the permanent magnet permanent magnet placed verticallyplaced vertically in a tube in a tube under the under the center of marine magnetic compasscenter of marine magnetic compass..

A. heeling magnet

B. fore and aft magnet

C. athwartship bar magnet

D. flinders bar

• 54. A curve passing through places 54. A curve passing through places where where there is neither dip northere is neither dip nor inclinations inclinations on the compass needle.on the compass needle.

A. magnetic equator

B. magnetic field

C. magnetic north

D. magnetic meridian

• 55. It is the tendency of a 55. It is the tendency of a gyroscope togyroscope to change from its original alignmentchange from its original alignment..

A. gyro drift

B. gyro error

C. toppling

D. torque

• 56. It is also known as 56. It is also known as two-axis two-axis gyroscopegyroscope where the gyro wheel is where the gyro wheel is mounted in two gimbals at right angles.mounted in two gimbals at right angles.

A. fixed mount gyroscope

B. rate gyroscope

C. position gyroscope

D. special gyroscope

• 57. It is a 57. It is a single axis gyro,single axis gyro, which consists which consists of a wheel mounted in one gimbal, the of a wheel mounted in one gimbal, the rotation of which is constrained by a rotation of which is constrained by a spring.spring.

A. position gyroscope

B. rate gyroscope

C. special gyroscope

D. free gyroscope

• 58. The 58. The greatest directive forcegreatest directive force is exerted is exerted on the magnetic compasson the magnetic compass when the: when the:

A. vessel is near the magnetic equator

B. needle are nearly in line with the

meridian

C. vessel is near the magnetic pole

D. variation is near zero

59. It is where the 59. It is where the gyroscope is mounted gyroscope is mounted to prevent it from precessingto prevent it from precessing..

A. wheels

B. axis

C. gimbals

D. gyro bowl

• 60. It is the 60. It is the effect on the gyro wheel if theeffect on the gyro wheel if the precession is preventedprecession is prevented and the gyro and the gyro wheel will offer no resistance to a torque.wheel will offer no resistance to a torque.

A. alignment effect

B. precession

C. gyro effect

D. toppling

• 61. It is the 61. It is the compass errorcompass error resulted from resulted from the the external or local magnetic attractionexternal or local magnetic attraction..

A. compass error

B. variation

C. deviations

D. gravitational effect

• 62. It is the term used 62. It is the term used when a force iswhen a force is applied on a gyroapplied on a gyro spinning in a spinning in a direction causing it to tilt.direction causing it to tilt.

A. toppling

B. precession

C. tilting force

D. torque

• 63. It is the 63. It is the gyroscope errorgyroscope error affected byaffected by meridian convergencemeridian convergence on a compass in on a compass in a a high-speed craft.high-speed craft.

A. apparent drift

B. tilting error

C. transport error

D. meridian error

• 64. It is a 64. It is a fly wheelfly wheel in a universal mounting in a universal mounting where the axis is free to point in any where the axis is free to point in any direction.direction.

A. gyroscope

B. compass bowl

C. gyrosphere

D. universal gimbal

• 65. It is a 65. It is a gyroscope error that affectsgyroscope error that affects the the heading system due to the rotation of heading system due to the rotation of the earth.the earth.

A. apparent drift

B. transport error

C. tilting error

D. gravity error

• 66. It is a 66. It is a gyro driftgyro drift when the when the gyroscope gyroscope isis subjected to an angular vibrationsubjected to an angular vibration..

A. tilting

B. aniso electricity

C. mechanical imperfections

D. dynamic unbalance

• 67. It is the 67. It is the gyro driftgyro drift caused bycaused by gimbal gimbal friction friction and also and also by electrical conductorsby electrical conductors that carry power to the motor of the that carry power to the motor of the wheel.wheel.

A. mechanical imperfections

B. aniso electricity

C. unbalance

D. dynamic drift

• 68. The gyro compass has the 68. The gyro compass has the least least directional powerdirectional power at: at:

A. latitude 45B. the equator

C. the pole

D. latitude 75

• 69. The 69. The pens in the gyro course pens in the gyro course recorderrecorder are attached to arms that are are attached to arms that are generally controlled bygenerally controlled by::

• A. the electrical charges of the gyro

• B. an indicator from the master compass

• C. speed adjustment of the master gyro

• D. the sensitive element

• 70. When a 70. When a gyro compass is operating gyro compass is operating properlyproperly, its , its rotor shaft is alignedrotor shaft is aligned in: in:

• A. N – E

• B. N – W

• C. N – S

• D. N – N

• 71. 71. Speed adjustment on the master Speed adjustment on the master gyrogyro should be should be made withinmade within _____ _____ knots.knots.

• A. 4 knots

• B. 5 knots

• C. 2 knots

• D. 3 knots

• 72. If the 72. If the rotor on a gyro is turning in rotor on a gyro is turning in the wrong directionthe wrong direction it will cause the it will cause the gyro to:gyro to:

• A. read reciprocal direction

• B. misaligned with the gyro direction

• C. precess with its position

• D. read 180º in error

• 73. To 73. To effect the symmetrical effect the symmetrical distribution of weight about the vertical distribution of weight about the vertical axis of a gyro compassaxis of a gyro compass the ____ is the ____ is added to the added to the vertical ringvertical ring..

• A. quadrantal sphere

• B. compensator weight

• C. sensitive element

• D. bearing circle

• 74. A circle tightly fitted on the 74. A circle tightly fitted on the compasscompass without an azimuth mirror without an azimuth mirror, , but but only sight vanesonly sight vanes will be: will be:

• A. pelorus

• B. azimuth circle

• C. bearing circle

• D. compass circle

• 75. If the 75. If the gyro is started with the south gyro is started with the south endend of the gyro rotor case toward the of the gyro rotor case toward the north, it will:north, it will:

• A. read 180º in reciprocal

• B. read at 000º at north end

• C. read 180º in error

• D. read at south end

• 76. If the 76. If the locking devices of the gyro in locking devices of the gyro in operation is left unlockedoperation is left unlocked, the gyro will , the gyro will cause ________.cause ________.

A. the compass to turn constantly and

becomes erratic

B. a variable error on the compass.

C. activation of the alarm

D. a constant error

• 77. The 77. The factor that produces oscillation factor that produces oscillation on the gyroon the gyro, creating , creating temporary temporary dislocation in its directional orientationdislocation in its directional orientation until it is oriented is _______.until it is oriented is _______.

• A. changes in course

• B. unsteady power supply

• C. change in speed

• D. directive force

• 78. The 78. The directive force of a gyro directive force of a gyro compasscompass ______. ______.

A. decreases with latitude being maximum

at the poles

B. increases with latitude being maximum

at the equator

C. remains constant at any latitude

D. is greatest when vessel is near the

magnetic equator

79. To 79. To maintain the gyro on its axismaintain the gyro on its axis, it , it must be must be capable ofcapable of ______. ______.

• A. gyroscopic inertia

• B. precession

• C. rigidity

• D. continuous spinning

• 80. The 80. The reaction of the gyro compass to reaction of the gyro compass to an applied forcean applied force is ______. is ______.

• A. gyroscopic inertia

• B. counter effect

• C. precession

• D. gravity effect

• 81. 81. MagnetismMagnetism which is present only which is present only when the when the material is under the material is under the influence of an external fieldinfluence of an external field..

• A. magnetic field

• B. permanent magnetism

• C. variation

• D. induced magnetism

• 82. _____ refers to any 82. _____ refers to any change in the change in the current supplied to the compass current supplied to the compass compensating coilscompensating coils to reduce to reduce degaussing errors.degaussing errors.

• A. compass compensation

• B. compass correction

• C. compass adjustment

• D. magnetic adjustment

• 83. There are several reasons for 83. There are several reasons for correcting the errors of the magnetic correcting the errors of the magnetic compass EXCEPTcompass EXCEPT::

A. magnetic compass is simple to use after correction

B. magnetic compass is easier to use if deviation are small.

C. even known and compensated for deviation, introduces error because the compass operates sluggishly and unsteadily when deviation is present.

D. even though the deviations are compensated for they will be subject to appreciable change as a function of heel and magnetic latitude.

• 84. In magnetism, this is the 84. In magnetism, this is the angle angle between the grid and the magnetic between the grid and the magnetic meridianmeridian at any place. at any place.

• A. grivation

• B. variation

• C. deviation

• D. dip

• 85. What do you call the angle between 85. What do you call the angle between the the lower branch of the geomagnetic lower branch of the geomagnetic meridian of a place and the geo-magnetic meridian of a place and the geo-magnetic over which the sun is locatedover which the sun is located??

• A. Variation

• B. Declination

• C. Magnetic dip

• D. Geo-magnetic time

• 86. What is the term on the 86. What is the term on the transient transient oscillatory gyro compass error that is oscillatory gyro compass error that is dependent upon the rate of change of dependent upon the rate of change of shipship’’s speed and courses speed and course??

• A. Damping error

• B. Deflection error

• C. Gimbaling error

• D. Quadrantal error

• 87. If the precession is prevented and 87. If the precession is prevented and the the gyro wheel will offer no resistance gyro wheel will offer no resistance to a torqueto a torque, what do you call this effect , what do you call this effect to the gyro wheel?to the gyro wheel?

• A. Precession effect

• B. Gyro drift

• C. Toppling effect

• D. Alignment effect

• 88. This is an error introduced on a 88. This is an error introduced on a gyrocompass by the gyrocompass by the tilting of the tilting of the mounting system of the compass due mounting system of the compass due to the horizontal acceleration caused to the horizontal acceleration caused the motion of the vesselthe motion of the vessel??

• A. Gimbaling error

• B. Quadrantal error

• C. Ballistic error

• D. Damping error

• 89. This is a device on a meridian gyro 89. This is a device on a meridian gyro that is located about the vertical axis of that is located about the vertical axis of the gyro, that the gyro, that applies torque about the applies torque about the vertical axisvertical axis proportional to tilt and proportional to tilt and causes the gyro to causes the gyro to precess about the precess about the horizontal axis to reduce the tilt to zerohorizontal axis to reduce the tilt to zero..

• A. levellling torquer

• B. azimuth control torquer

• C. vertical torquer

• D. phantom

• 90. This is the 90. This is the remote indicating gyro-remote indicating gyro-stabilized earth induction compassstabilized earth induction compass that that senses the horizontal component of the senses the horizontal component of the earthearth’’s magnetic field?s magnetic field?

• A. Speed gyro compass

• B. Gyro flux – gate compass

• C. Horizontal gyro compass

• D. Remote-stabilized gyro compass

• 91. In 91. In adjusting the magnetic compass,adjusting the magnetic compass, which of the following would you which of the following would you eliminate the mosteliminate the most??

• A. Compass Error

• B. Variation

• C. Deviation

• D. Magnetic field

• 92. What is the 92. What is the most accurate most accurate deviation diagram used on boarddeviation diagram used on board??

• A. Algebraic diagram

• B. Reciprocal diagram

• C. Deviation diagram

• D. Napier’s diagram

• 93. The angular 93. The angular deflection of the deflection of the compass needle as affected by the compass needle as affected by the EarthEarth’’s polarity.s polarity.

• A. variation

• B. deviation

• C. magnetic field

• D. deflection error

• 94 The tendency of the 94 The tendency of the spinning wheel spinning wheel to maintain the direction of its plane of to maintain the direction of its plane of rotation in spacerotation in space..

• A. Flywheel

• B. Rigidity

• C. Precession

• D. Inertia

• 95. The combined effect of horizontal 95. The combined effect of horizontal plane sub – permanent magnetism of a plane sub – permanent magnetism of a ship and the ship and the magnetism induced by magnetism induced by vertical soft ironvertical soft iron and component of the and component of the EarthEarth’’s force is called;s force is called;

• A. Magnetic polarity

• B. Quadrantal deviation

• C. Coefficient magnetism

• D. Semi – circular deviation

• 96. What is the 96. What is the purpose of the liquid purpose of the liquid inside the magnetic compassinside the magnetic compass??

• A. Better attractive force on magnetic pole

• B. There will be a steady effect on the

compass card

• C. To prevent the compass from freezing

• D. None of these

• 97. The 97. The compass heading of the vessel compass heading of the vessel differ from the true headingdiffer from the true heading due to; due to;

• A. Compass error

• B. Variation

• C. Deviation

• D. Magnetic dip

• 98. In compass magnetism the word 98. In compass magnetism the word ““secular changesecular change”” means; means;

• A. The reading from the compass rose

• B. Changes of magnetism within the ship

• C. Computing for yearly deviation table

• D. The yearly change of variation in the

locality

• 99. 99. Gyrocompass is reliableGyrocompass is reliable up to; up to;

• A. All latitudes

• B. Latitude 75º N or S

• C. Latitude 90º N or S

• D. Latitude 60º N or S

• 100. As your vessel 100. As your vessel approaching the approaching the magnetic equatormagnetic equator, what is , what is true true concerning the deviationconcerning the deviation due to the due to the permanent magnetism o the ship?permanent magnetism o the ship?

• A. Does not change

• B. Appreciably change

• C. Decreases

• D. Increases